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Do Fuels Made From Plastic Make Eco Sense?

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Chemical recycling involves sorting plastic by type, grinding into powders, and mixing and melting into the same kind of polymers from which the powders were generated. sturti / Getty Images

By Brigitte Osterath

Yogurt pots, shampoo bottles, coffee-to-go lids, bubble wrap — plastic products are all composed of the same building blocks: long carbon chains.

Heating them to high temperatures makes the carbon chains crack into a mixture of shorter molecules, ultimately converting them back into crude oil, the resource from which the majority of plastic products were originally made.



Varying the process can result in different carbon chain lengths and therefore different carbon-based products, ranging from fuels such as diesel and kerosene to petroleum naphtha, a valuable liquid for the chemical industry.

This potential mode of recycling — where plastic is broken down into its original components — has been becoming increasingly popular in industry.

It's known as 'chemical recycling,' as opposed to 'mechanical recycling' — the chop-and-wash-method in which plastic is sorted by type, ground into powders, mixed and melted into the very same kind of polymers from which the powders were generated.

"Chemical recycling has emerged as a major topic [in industry], mainly out of helplessness of how to proceed in mechanical recycling," says Thomas Fischer, head of the recycling management division with the non-profit environmental association Deutsche Umwelthilfe.

A prerequisite for mechanical recycling, he says, is making plastic that is actually recyclable. "That requires a lot of know-how, such as which dyestuffs and additives can be used and which cannot."

You also have to design the product itself in a certain way. When a product has been manufactured by layering several different polymers on top of each other, for example, recycling becomes tricky.

Chemical recycling is much simpler — it's just a case of heating everything with no need for prior sorting. That's the idea at least.

Big Business

Several companies have made significant investments in chemical recycling, building facilities to test various ways of making what is allegedly more environmentally friendly oil. So far, it's still in the development and test stage.

In 2018, multinational chemistry giant BASF launched ChemCycling — a project that aims to generate a so-called pyrolysis oil from plastic waste. The company claims it can be used in the production of new polymers, which it says will save fossil fuel resources.

Austrian oil and gas company OMV has built a pilot plant which it says can process all common packaging material such as polyethylene, polypropylene and polystyrene.

The plastics are chopped down, mixed with a high-boiling solvent and heated in a furnace at over 300 degrees Celcius (572 degrees Fahrenheit). Once the product has been distilled and the solvent filtered off, the company is left with synthetic crude oil, which it claims is "free of sulfur, lighter than fossil crude oil and with a higher hydrogen content — therefore of higher quality."

The product can be refined to make fuels such as gasoline, kerosene and diesel or petrochemical products.

The plant has the capacity to convert 100 kilos of waste each hour, OMV told DW. But a planned successor facility would be able to process 2,000 kilos hourly.

Similar pilot plants are being constructed in other countries across Europe.

Behind the Hype

So, can chemical recycling solve our waste problem through the creation of fuels?

Roman Maletz, a researcher at the Institute of Waste Management and Circular Economy at the Technical University in Dresden, is not convinced.

The idea of recycling plastic trash by cracking it, he says, is neither new nor revolutionary. It has just never worked before.

"In the past, such plants always ran into problems when in continuous operation," Maletz said. "I don't see how these issues could suddenly be resolved."

Problems arise when the trash contains too many different materials or when it is too dirty.

"In that case, the quality of the product is lowered, and the whole process becomes economically unviable."

Moreover, it is not necessarily environmentally friendly, adds Henning Wilts, Director of the Circular Economy Division at Wuppertal Institute for Climate, Environment and Energy.

"If you break waste apart at a molecular level, you need a lot of energy, so the CO2 savings are quite low," he tells DW. "If the energy needed comes from burning coal, then the whole thing is an environmental disaster."

Although it is expensive, he says mechanical recycling still remains the recycling of choice.

"If countries use the existence of chemical recycling as an excuse to stop any efforts in mechanical recycling, that will become a problem."

He says the fact that petroleum naphtha generated from chemical recycling could be used to produce new food-grade plastics which is "one of the big drivers to develop the technology."

Producing fuels like diesel or kerosene from plastic trash, however, Fischer says, makes less sense.

"If fuels are produced which are burned afterwards, then even more CO2 is blown into the air," Fischer explains. "That's not the idea of a cycle."

Reposted with permission from Deutsche Welle.

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A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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